V 


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THE  EXTRACTION  AND  PURIFICATION 
OF  CAESIUM  SALTS 


BY 


JOHN  DRISCOLL  CONATY 


THESIS 


FOR  THE 


DEGREE  OF  BACHELOR  OF  SCIENCE 

IN 

CHEMISTRY 


COLLEGE  OF  LIBERAL  ARTS  AND  SCIENCES 

UNIVERSITY  OF  ILLINOIS 


1922 


to 


UNIVERSITY  OF  ILLINOIS 


i92_2__ 

THIS  IS  TO  CERTIFY  THAT  THE  THESIS  PREPARED  UNDER  MY  SUPERVISION  BY 

JQHK_DftI_SC_OLL_C^^^  

ENTITLED__THS_MTMQTI_Qli_ANp__PURl£XCMIM__QF_Cj^_SIU^^  


IS  APPROVED  BY  ME  AS  FULFILLING  THIS  PART  OF  THE  REQUIREMENTS  FOR  THE 
DEGREE  OF Bac_he_lo_r  p_f__Scjience__i^^^^^  


Instructor  in  Charge 


Approved  : 


/I  Ct  / q HEAD  OF  DEPARTMENT  OF C_HEMI_ST_RY_ 


i 


Digitized  by  the  Internet  Archive 

in  2016 


https://archive.org/details/extractionpurifiOOcona 


Acknowledgement . 

The  author  wishes  to  ta,ke  this  opportunity  to 
express  his  sincere  thanks  to  Professor  B.S.  Hopkins 
at  whose  suggestion  this  work  was  carried  out  and  to 
whose  aid  and  advice  its  successful  completion  is 
largely  due. 


Tabla  of  Contents. 


I.  Historical 

II.  3xtraction  of  Caesium  from  Hollucita 

A.  Decomposition  of  the  Llaterial 

B.  Precipitation  of  Caesium  as  the 

Double  Lead  Salt  According  to  the 
Method  of  ¥ells.  Page  2. 

e.  Precix-)i  tation  of  Caesim  as  the 
Double  Antimony  Salt  According  to 
the  Method  of  Godeffroy  Page  3. 

D.  Discussion  of  the  Results  and 

Precautions  Page  3. 


Page  1. 


Page  2. 


E.  Diagram  of  Method  for  the 

Extraction  of  Caesiura  from 
Pollucite  as  Cs^Sb^Clg  Page  5. 

III.  PractionG.1  Crystallization  of  the 
Alums  of  the  Alkali  Metals 

A.  Historical  Page  6. 

B.  Plan  for  Systematic  Practional 
Crystallization  of  the  Alkali 

Metals  Page  7. 

C.  Results  Obtained  fro.m  Praction- 

ation  Page  8. 

D.  Solubility  of  cs  and  Rb  in  the 

Presence  of  yunmoniua  Alum  Page  9. 


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IV.  Surmnary 


Page  10 


References 


Page  11 


V 


Th9  "Extraction  and  Purification 
of  Caesium  Salts. 

Hi storical 

In  1860  Bunsen  and  G.  Hirchluof f wnils  investigating  tne 
mineral  waters  of  Burkheim  evaporo.ted  dovm  forty  tons  of 
v/ater  and  removed  tlie  alkaHi  eartiis  and  lithia  witn  ammonium 
carbonate.  The  filtrate  snov/ed  tjie  spectral  lines  tor  sodi’um, 
potassium  and  litnium,  “and,  "besides  tnese,  tv/o  splendid  lines 
near  the  blue  strontum  line  Bunsen  and  Kirchiiolf  add: 

“As  no  elementar3,'  oody  produces  two  blue  lines  in  tni  s 
portion  of  the  spectru.'a  we  may  consider  tne  existence  of  tni  s 
Hitherto  unknown  alkaline  element  was  placed  beyond  doubt. 

The  tacility  witii  whicn  a few  tnousandtns  of  a miliigrtim  of 
tni  s bod;^’"  may  be  recognized  by  tne  brigiit  blue  of  its  in- 
candescent vapor  even  wnen  mixed  witn  large  quantities  of 
more  common  alkalies,  has  induced  us  to  propose  for  tne  name 
caesium  (and  tiie  ^'mbol  (js)  derived  from  tne  Latin  caeslus, 
used  to  designate  tne  blue  of  tne  clear  sky". 

Caesium  is  found  widely  distributed  in  nature  in  small 
amounts  Lepidolite  (Li ,E,Na,F,Al(Si03) j)  a mineral  occurring 
in  considerable  quantities  near  Pala,  San  Diego  Co.,  Calif., 
also  at  Paris  and  nebron,  :ie . , contains  from  .3-1%  Cs^O. 
Pollucite  a mineral  occurring  on  tne  island  of  Elda  and  at 
Hebron,  Me,,  contains  from  30-35%  CS2O  . 


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2. 

^traction  of  Caesium  from  Pollucita 
Decomposition  of  tlie  Material 
Tile  mineral  was  finely  pulverized  by  grinding  in  a Ijall 
mill,  placed  in  large  evaporating  disn.es  and  digested  from 
48  to  60  hours  v/itn  dilute  nydrocnioric  acid  (sp.gr.  I.l2). 

At  the  end  of  this  period  tne  mixture  was  evaporated  to  di%*- 
ness  on  tne  water  datn  alter  wnicn  it  was  carefully  heated 
over  a free  flame  to  dehydrate  tne  silicic  acid.  The  material 
was  then  taken  up  with  v/ater  and  enough  dilute  hydrochloric 
acid  added  to  dissolve  the  iron  salts,  and  the  silica  filtered 
off . 

Precipitation  of  Caesiun  as  the 
Double  Lead  8alt  According  to  the  Method 
of  Wells 

Several  methods  are  described  in  the  literature  for  the 
isolation  of  caesium  from  the  nydrocnioric  acid  extract.  Wells'^ 
has  recommended  the  use  of  tne  yellov/  salt  2CsCl  PbCl^  in 
which  tne  precipitation  is  made  by  adding  a hot  concentrated 
solution  of  tne  calculated  amount  of  lead  nitrate  to  the  crude 
hydrochloric  acid  extract.  Chlorine  gas  is  then  passed  in 
until  the  solution  is  saturated.  After  allowing  to  stand  for 
ten  to  twelve  hours  tne  solution  is  decanted  from  the  pre- 
cipitate of  2GsCl  PbCl^.  Tne  precipitate  is  then  boiled  with 
ammonium  carbonate  after  which  the  Pb  O2  filtered  off. 

only  one  run  was  made  on  a samx^ls  of  Maine  pollucite  as 
tne  yield  of  caesiuia  chloride  v/as  veiy  small  as  compared  with 
the  heavy  and  large  amount  of  precixJitate  forraed  and  the 


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dil’ficulty  in  v;orking  v/itJri  free  chlorine. 


Precipitation  of  caesium  as  the 
Double  Antimony  Salt  According  to  the 

Method,  of  Godeffroy.  | 

i 

A veiy  le.rge  series  of  salts  are  known  of  the  general  | 

type  R M X where  R is  potassium,  caesium  or  ammoniiirij , I'  a | 

{• 

f 

heav;^^  metal  antimony,  arsenic,  mercury'  or  copper,  and  A a | 

halogen.  ! 

Many  years  ago  Godefiroy^  recoiamended  tiie  extraction  of 
caesium  as  the  double  salt  of  antimony  prepared  by  trea.ting 
the  hydrochloric  acid  extract  with  a strong  hot  solution  of 
antimony  trichloride  tne  pale  yellow  salt  3CsCl  2SbCl-z  having 
definite  crystalline  form,  sepa.rating  out  on  cooling.  This 
salt  v/as  filtered  on  Buchner  funnel,  a.nd  v, 'ashed  vifch  dilute 
hydrochloric  acid  after  which  it  was  suspended  in  v/ater  and 
at  first  was  decomposed  with  hydrogen  sulfide,  but  a.s**this 
consumed  too  long  a time  it  v;as  in  subsequent  runs  decomposed 
by  boiling  with  dilute  ammonium  hydroxide,  the  antimonous 
oxide  being  filtered  off.  The  solution  of  mixed  chlorides 
was  then  evapora.ted  to  a small  volume,  nitric  acid  added  and 
the  evaporation  taken  to  dryness^.  The  fused.  nitre.te  v/as  then 
recry' stall  i zed.  from  hot  v/ater  from  v/hich  it  crystallized  out  in 
large  prisms  like  potassium  nitrate. 

Discussion  of  the  Results  and  Precautions. 

The  maximum  yield  of  crystallized,  caesium  nitrate  that  was 
obtained  by  this  method  was  7%,  but  this  low  yield  we,s  due  to 
a poor  grade  of  pollucite  as  the  solutions  that  were  decanted 
from  tne  caesium  antimony  chloride  precipitate  were 


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4. 


found  to  have  only  traces  of  caesium  remaining  in  them,  since 
it  was  found  impossible  to  obtain  arry  of  the  double  lead  salt 
irom  this  solution,  the  latter  being  tne  more  insoluble  of  the 
two  salts. 

In  tne  precipi te.tion  of  the  3Cs  Cl  2SbCl„  salt  Groups  I,  ll, 

o 

III  and  Iv  metals  do  not  interfere  as  the  racid  concentration 
is  sufficient  to  maintain  their  solution.  If  the  iron  were  removed 
as  the  hydroxide,  large  quantities  of  caesium  v/ould  be  lost 
due  to  occlusion  unless  the  ferric  hydroxide  be  reprecipitated 
several  times. 


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1‘S^v.--;  ' 


5 


Diagram  of  K<9thod  for  the 
ijjxtraction  of  Caesian  from  Pollucite 
as  GSjSb^Clg 


SiO^  ^tc. 


Pollucit e 

Boil  HCl  sp.gr. 1.12  48-60  hours 

Uvaporatiou  and  Filtration 


Solution;  Alkali  ..petals, 


CsCl  PbO. 


Recr>"  stall!  zed 


from  hot  water 


6 


Fractional  stall izat ion  of  the 
Alums  of  the  Alhali  Metals. 

The  soluhilities  of  the  alums  of  sodium,  ammoniura, 
potassium,  caesium  and  rubidium  as  stated  in  Comey  are  as 
f ollov/s: 


Parts  in  100  Parts  V/ater 

T «mp . 

Pota.ssi'om  alum 

13.5 

17® 

Ammonium  alum 

8.74 

17.5 

SodiuTi  alun 

103.1 

10® 

Rubidium  alum 

2.27 

I7P 

Caesium  alum 

0.619 

17® 

Rohinson  and  Hutchins^  v/ere  the  first  to  point  out 
this  difference  in  solubility  and  recommended  it  as  a me.ans 
of  separating  caesium  and  rubidium  from  lithiun  and  potassium 
in  lepidolite  after  the  mineral  had  been  decomposed  v\ritn 
hydrofluoric  acid.  They  also  pointed  out  the  difference  in 
solubility  of  caesium  and  ruoidiuin  alums  and  recommended  a 
fractional  crystallization  for  the  separation  of  these  elements. 
Hov;ever,  tne  difference  in  solubility  of  ca.esiua  and  rubidium 
aluas  is  not  great  enough  to  allovr  a rapid  separation  of 
these  elements,  v/hile  the  difierence  in  solubility  of  the  alums 
of  the  rare  metals  and  those  of  the  common  ones  is  suificient 


to  make  a sati sfactoiy  method  of  separation. 


7. 


Plan  for  Systematic  Practional  cry atallizc tion 
of  Alums  01  tne  Alkali  Metals. 

i 

M 


The  pollucite  was  decomposed  in  tne  usual  manner  with  | 
ny drocnloric  acid  and  after  evaporation  and  filtro,tion  of  | 

tne  silica  the  hydrochloric  acid  extract  was  concentre  ted  i 

witn  sulfuric  acid.  On  cooling  the  mixed  aluius  ciystaliized  | 

r 

out.  'i'nis  is  the  most  advantageous  and  rapid  method  to  ( 


remove  caesiuiri  from  pollucite.  The  mixed  alums  vdiile  con-  ! 

f 

taining  traces  of  iron  were  in  two  to  three  ciy  stallizations  t 
free  from  iron. 


s. 


Tile  alujTis  (1)  from  3400  grams  of  pollucite  containing 
approximately  12/^  CS2O  were  subjected  to  ^'Stematic  fra.ctional 
cry  stall  iza,ti  on  by  dissolving  in  not  water  and  stirring 
vigorously  wnile  tii9  solution  yjaz  cooling  to  destroy  the 
supersaturated  solutions  which  these  alums  especially  caesium 
tend  to  form.  The  motner  liquor  v/as  concentrated  until  on 
cooling  it  yielded  a second  crop  of  ci^’stjils,  (6)  and  the 
ne\7  mother  liquor  concentrated  again  to  yield  a third  crop 
of  cr;>’stals  (12)  and  so  on.  The  crystals  in  the  first 
crystallizing  disn  (2)  were  d.issolved  in  not  water  and  allow- 
ed to  crystallize  again  (4)  the  supernatant  liquid  (5)  being 
used  to  dissolve  the^  second  crop  of  cr;>'stals  (6)  and 
allowed  to  re cr;>' stall ize  tni  s scheme  being  continued  in  all 
the  dishes.  The  cr;>*stals  separa.ting  in  the  first  dish  wrere 
repeatedly  recrystallized  from  hot  v/ater.  By  tnis  system 
tne  cry^stals  in  tne  first  of  the  series  were  tJie  more 
insoluble  alur^s  of  caesium  (and  rubidium)  while  those  in 
tne  lov\rer  end  of  tne  series  were  tne  more  soluble  alums 
namely  sodium  and  potassium. 

Results  Obtained  from  Rractionation 
of  the  Alums. 

After  the  alums  from  the  pollucite  were  recrystallized 
nine  times  the  crystals  in  the  insoluble  end  of  tne  series 
gave  strong  tests  for  caesium  and  traces  of  sodium,  and 
potassium  while  the  crystals  in  the  more  soluble  end  (ninth 
dish)  gave  strong  tests  for  sodium  and  potassium  a.nd  traces 
of  caesium. 


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- — -=^ ' 97 

T}i9  material  vaiicii  was  ricn-^st  in  ca=?sium  was  then 
subjected  to  fractional  cr;>' stallization  v/ith  the  object  of 
separating  any  rubidium  that  might  be  present.  After  the 
process  of  ciy' stall i aati on  was  carried  througii  twenty-four 
crystallizations  the  spectruLu  saioived  no  evidence  of  tne 
presence  of  rubidium  in  the  tv/enty -fourth  dish  v/hile  the  first 
dish  showed  nearly  pure  caesium  with  traces  of  sodium. 

Solubility  of  Caesium  and  Rubidium  in  the  Presence 

of  Ammonium  Alum. 

7 

browning  and  Spencer  have  determined  the  solubility 
of  caesium  ana  rubidiuiL  in  a saturated  solution  of  ammonium 
aluiii.  They  found  that  Ic.c.  of  a solution  of  RbCl  containing 
0.0002gm.  v.'ould  give  a perceptible  precipitate  v/hen  treated 
with  5c. c.  of  a saturated  solution  of  ammonium  alum  and  that 
Ic.c.  of  a csCl  solution  containing  .00005gm.  cs  v/ould  give 
a precipitate  of  caesiun}  a.lum. 


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TOT 


BuiWiary . 

A study  of  the  various  methods  for  the  decomposition 
of  pollucite  was  mo.de,  and  the  various  ways  of  isolating 
caesium  from  the  acid  extract.  This  worh  seems  to  suggest 
that  the  most  convenient  method  for  the  isoia.tion  of  caesium 
is  as  the  alum  by  concentrating  acid  solutions  with  sulfuric 
acid.  It  has  the  advantage  over  precipitations  of  douuie 
metallic  salts  in  avoiding  the  decomposition  of  these  with 
hydrogen  sulfide  or  ammonium  hydroxide  and  in  being  a more 
insoluble  salt  tha.n  the  double  metallic  halides. 


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